Solution structure of human myeloid-derived growth factor suggests a conserved function in the endoplasmic reticulum

Valeriu Bortnov,Marco Tonelli,Alex Bateman,Omar N Demerdash,Julie C Mitchell,Douglas S Annis,Deane F Mosher,Woonghee Lee,Ziqing Lin,Ying Ge,John L Markley

doi:10.1038/s41467-019-13577-5

Abstract

Human myeloid-derived growth factor (hMYDGF) is a 142-residue protein with a C-terminal endoplasmic reticulum (ER) retention sequence (ERS). Extracellular MYDGF mediates cardiac repair in mice after anoxic injury. Although homologs of hMYDGF are found in eukaryotes as distant as protozoans, its structure and function are unknown. Here we present the NMR solution structure of hMYDGF, which consists of a short α-helix and ten β-strands distributed in three β-sheets. Conserved residues map to the unstructured ERS, loops on the face opposite the ERS, and the surface of a cavity underneath the conserved loops. The only protein or portion of a protein known to have a similar fold is the base domain of VNN1. We suggest, in analogy to the tethering of the VNN1 nitrilase domain to the plasma membrane via its base domain, that MYDGF complexed to the KDEL receptor binds cargo via its conserved residues for transport to the ER.

Highlights

Human myeloid-derived growth factor is a 142-residue protein with a C-terminal endoplasmic reticulum (ER) retention sequence (ERS)
We demonstrate that the face of Human myeloid-derived growth factor (hMYDGF) predicted to interact with KDELRs is perturbed by changes in pH, whereas residues conserved in MYDGF homologs are clustered on the opposite face
To evaluate whether hMYDGF folded and purified by this method has the same structure as hMYDGF processed through the ER, we compared the bacterially expressed protein to hMYDGF secreted from High Five insect cells

Summary

Introduction

Human myeloid-derived growth factor (hMYDGF) is a 142-residue protein with a C-terminal endoplasmic reticulum (ER) retention sequence (ERS). In analogy to the tethering of the VNN1 nitrilase domain to the plasma membrane via its base domain, that MYDGF complexed to the KDEL receptor binds cargo via its conserved residues for transport to the ER. Human myeloid-derived growth factor (hMYDGF) is a member of the widely distributed MYDGF family of proteins found in organisms as distant as protozoans[1]. Experiments appending candidate endoplasmic reticulum (ER) retention sequences (ERS) to the C-terminus of a model secreted protein for expression in HeLa cells demonstrated that RTEL binds to human KDEL receptors KDELR1, KDELR2, and (to a lesser extent) KDELR3 In analogy to vanins, that MYDGF complexed to KDELRs binds cargo via its conserved residues for transport to the ER

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Conclusion